diff options
| author | Florian Westphal <fw@strlen.de> | 2023-03-24 11:47:20 +0100 |
|---|---|---|
| committer | Kevin Wolf <kwolf@redhat.com> | 2023-03-27 13:44:29 +0200 |
| commit | bd2cd4a441ded163b62371790876f28a9b834317 (patch) | |
| tree | 0dd59ed051aac73435ed6b2a4a09f23506b83dc7 /nbd | |
| parent | e3debd5e7d0ce031356024878a0a18b9d109354a (diff) | |
nbd/server: push pending frames after sending reply
qemu-nbd doesn't set TCP_NODELAY on the tcp socket.
Kernel waits for more data and avoids transmission of small packets.
Without TLS this is barely noticeable, but with TLS this really shows.
Booting a VM via qemu-nbd on localhost (with tls) takes more than
2 minutes on my system. tcpdump shows frequent wait periods, where no
packets get sent for a 40ms period.
Add explicit (un)corking when processing (and responding to) requests.
"TCP_CORK, &zero" after earlier "CORK, &one" will flush pending data.
VM Boot time:
main: no tls: 23s, with tls: 2m45s
patched: no tls: 14s, with tls: 15s
VM Boot time, qemu-nbd via network (same lan):
main: no tls: 18s, with tls: 1m50s
patched: no tls: 17s, with tls: 18s
Future optimization: if we could detect if there is another pending
request we could defer the uncork operation because more data would be
appended.
Signed-off-by: Florian Westphal <fw@strlen.de>
Message-Id: <20230324104720.2498-1-fw@strlen.de>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'nbd')
| -rw-r--r-- | nbd/server.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/nbd/server.c b/nbd/server.c index a4750e4188..848836d414 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -2667,6 +2667,8 @@ static coroutine_fn void nbd_trip(void *opaque) goto disconnect; } + qio_channel_set_cork(client->ioc, true); + if (ret < 0) { /* It wasn't -EIO, so, according to nbd_co_receive_request() * semantics, we should return the error to the client. */ @@ -2692,6 +2694,7 @@ static coroutine_fn void nbd_trip(void *opaque) goto disconnect; } + qio_channel_set_cork(client->ioc, false); done: nbd_request_put(req); nbd_client_put(client); |